Robert Louis Stevenson's novella "Dr. Jekyll and Mr. Hyde" has been filmed multiple times. At the time of the the printing, "The Strange Case of Dr. Jekyll and Mr. Hyde" was more of a mystery novella and the surprise ending was that Dr. Jekyll WAS Mr. Hyde. Movie adaptation probably surrendered the surprise ending to popular culture.
John Barrymore portrayed Dr. Jekyll in this 1920 silent version. A renown actor from the stage, Barrymore captures a trick that he would have probably performed on stage, transferring from Jekyll to Hyde without make-up. given the sophistication of the cinema and stage shows of the time, this performance is a tour de force.
Sadly, the additional music to this silent film mars the production values. The organ music sounds like something the Church Lady would play.